Light emitting device

ABSTRACT

A light emitting device includes a substrate and a light emitting unit. The light emitting unit is over the substrate. The light emitting unit includes a light emitting subpixel and an electrode. The electrode is stacked on the light emitting subpixel along a direction. Moreover, the electrode includes a dimension measured perpendicular to the direction and the dimension is not greater than about 8 um.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority of U.S. Provisional PatentApplication Ser. No. 62/487,097, filed on Apr. 19, 2017, which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure is related to light emitting device, especiallyto an organic light emitting device and manufacturing method thereof.

BACKGROUND

Flat panel display becomes more popular in recent years and is widelyadopted from pocket sized electronic devices, such as cell phone, to awall mount big screen television. Similar to the increasing demanding onthe transistor density for IC (Integrated Circuit), the resolutionrequirement for a display has also been elevated. In recent trend,organic light emitting material is introduced as a light source in flatpanel to enhance the possibility of foldability. To select the electrodefor the organic light emitting material is challenge to a flexible paneldesigner. For most flat panels, ITO or IZO are commonly used as a topelectrode for the lighting source when considering transparency andresistivity. However, the poor performance on flexibility is a concernwhen the panel is deformed.

SUMMARY

A light emitting device includes a substrate and a light emitting unit.The light emitting unit is over the substrate. The light emitting unitincludes a light emitting subpixel and an electrode. The electrode isstacked on the light emitting subpixel along a direction. Moreover, theelectrode includes a dimension measured perpendicular to the directionand the dimension is not greater than about 8 um.

In some embodiments, the electrode is a cathode of the light emittingunit. The light emitting device further includes an optical sensoradjacent to the light emitting unit and configured to detect emissionintensity of the light emitting unit.

In some embodiments, the light emitting device further includes an arrayof thin film transistors (TFT) under the light emitting unit and theoptical sensor is electrically connected to the TFT. The light emittingdevice further includes a stopper adjacent to the light emitting unit,wherein, along the direction, the stopper has a thickness being greaterthan a thickness of the light emitting unit. In some embodiments, thelight emitting device further includes a through via in the stopper.

In some embodiments, a light emitting device includes a substrate and anarray of light emitting units over the substrate. Each light emittingunit of the array includes an electrode and a light emitting layerbetween the electrode and the substrate, wherein a top view area of theelectrode is substantially equal to a top view area of the lightemitting layer.

In some embodiments, the light emitting device further includes aninsulation material filling a space between adjacent light emittingunits. The light emitting device further includes a conductive trace toconnect electrodes in a string. The light emitting device furtherincludes an array of optical sensors, wherein each of the opticalsensors is assigned to a corresponding light emitting unit. In someembodiments, the light emitting device further includes an array ofstoppers, wherein each stopper is between two adjacent light emittingunits. In some embodiments, the light emitting device further includes aconductive trace electrically connecting each optical sensor to acircuit in the substrate. In some embodiments, the light emitting devicefurther includes a touch sensor over the array of light emitting units,and an insulation layer between the touch sensor and the array of lightemitting units.

In some embodiments, the light emitting device further wherein the touchsensor is surrounded by a plurality of light emitting units from a topview perspective. In some embodiments, the light emitting device whereinthe touch sensor is laterally offset from the plurality of lightemitting units from a top view perspective. In some embodiments, thelight emitting device further includes an array of optical sensors overthe array of light emitting units, wherein the array of optical sensorsare configured to detect ambient light emitted into the light emittingdevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flexible light emitting device.

FIG. 2 is top view of a portion of a flexible light emitting deviceaccording to an embodiment.

FIG. 3 is top view of a portion of a flexible light emitting deviceaccording to an embodiment.

FIG. 4 is cross sectional view of a portion of a flexible light emittingdevice according to an embodiment.

FIG. 5 is cross sectional view of a portion of a flexible light emittingdevice according to an embodiment.

FIG. 6 is cross sectional view of a portion of a flexible light emittingdevice according to an embodiment.

FIG. 6A is cross sectional view of a portion of a flexible lightemitting device according to an embodiment.

FIG. 7 is cross sectional view of a portion of a flexible light emittingdevice according to an embodiment.

FIG. 8A is cross sectional view of a portion of a flexible lightemitting device according to an embodiment.

FIG. 8B is cross sectional view of a portion of a flexible lightemitting device according to an embodiment.

FIG. 9 is cross sectional view of a portion of a flexible light emittingdevice according to an embodiment.

FIG. 10 is top view of a portion of a flexible light emitting deviceaccording to an embodiment.

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure is to introduce a method being capable ofmanufacturing a high density light emitting display. In the disclosure,the term “high density” is defined as the lighting pixel density is atleast equal or greater than 800 ppi. However, the method is also appliedfor light emitting display with pixel density lower than 800 ppi.

The present disclosure is to provide a new design of an electrode for anorganic light emitting material used in a flexible panel. The electrodehas a suitable dimension is order to minimize the reflection of theambient light. Material of the electrode also has a high flexibility andlow resistivity so as to make the flexible panel foldable and low powerconsumption. Through the present disclosure, a flat panel designer canhave a much greater window to allocate the driving circuit, touch panelwires within the light emitting pixel array.

FIG. 1 illustrates an embodiment of an electronic device 10. Theelectronic device 10 can be a rigid or a flexible display. Display 10can have at least four different layers substantially stacked along athickness direction X. Layer 12 is a substrate configured as a platformto have a display layer 14 disposed thereon. Layer 16 is a cap layer tobe disposed on the light emitting layer 14 and layer 18 is configured asa window for light emitting in/out the electronic device 10. In someembodiments, layer 16 is an encapsulation layer. Layer 18 can also beconfigured as a touch interface for the user, therefore the surfacehardness of the might be high enough to meet the design requirement. Insome embodiments, layer 16 and layer 18 are integrated into one layer.

Layer 12 might be formed with a polymer matrix material. Layer 12 has aminimum bend radius around about 3 mm. The minimum bend radius ismeasured to the inside curvature, is the minimum radius one can bendlayer 12 without kinking it, damaging it, or shortening its life. Insome embodiments, several conductive traces may be disposed in layer 12and form circuitry to provide current to the light emitting layer 14. Insome embodiments, a thin film transistor (TFT) is disposed on layer 12and located between layer 12 and light emitting layer 14. In someembodiments, the TFT can be embedded into layer 12 and integrated as awhole.

FIG. 2 is a top view of the light emitting layer 14 in one embodiment.The light emitting layer has a surface 140. An array of light emittingunits including light emitting unit 145 a, 145 b, and 145 c disposed onthe surface 140. Each light emitting unit is supplied with currentthrough conductive trace 142. In one embodiments, some light emittingunits such as 145 a, 145 b, and 145 c are arranged in a column andconnected in series by the conductive trace 142. The serial connectedlight emitting units can be further electrically connected with anelectrode 146. The electrode 146 may be disposed at a peripheral regionof the surface 140. The substrate layer 12 may be disposed under thelight emitting layer 14.

FIG. 3 is a top view of the light emitting layer 14 in anotherembodiment. In addition to the light emitting units, a stopper 147 isdisposed between two adjacent light emitting units. In anotherembodiment, an optical sensor 150 is also disposed adjacent to a lightemitting unit. In some embodiments, the optical sensor 150 is disposedon al stopper 147 (as shown in the lower left corner). In someembodiments, a circuitry 156 configured to drive the array of lightemitting units is on the surface 140 and inserted between the lightemitting units.

FIG. 4 is a cross sectional view along line AA in FIG. 2. A layer 12 ahaving TFT or other circuitries can be disposed on the substrate 12. Atop surface of the layer 12 a is configured as a surface 140 for thelight emitting layer. There are two light emitting units 145 disposed onthe surface 140. Each light emitting unit has a light emitting subpixel145-2 and an electrode 145-1 disposed over the light emitting subpixel145-2.

Electrode 145-1 provides electric current to the light emitting subpixel145-2. The light emitting subpixel 145-2 can emit light through theelectrode 145-1 and also emit through layer 16 and layer 18, thenreached user's eyes. In some embodiments, the electrode 145-1 is acathode connected to the light emitting subpixel 145-2. As shown in FIG.2, in some embodiments, each electrode 145-1 is connected to aconductive trace 142 in order to provide electric current to acorresponding light emitting subpixel 145-2.

Electrode 145-1 includes conductive material and in some embodimentselectrode 145-1 includes metallic elements such as Mg, Al, Ag, Au, Cu,W, etc. In some embodiments, electrode 145-1 substantially includes Agand Mg.

Electrode 145-1 has a thickness d vertical to the surface 140. Thethickness d is designed to have a transmittance around 80% for the lightemitting from the light emitting subpixel 145-2. Moreover, the thicknessd might be adjusted according to the wavelength of the light emittingfrom a corresponding light emitting subpixel, which is located rightbetween the electrode 145-1 and the substrate 12. In some embodiments, athickness of electrode 145-1 is between about 200 Å and about 400 Å. Insome embodiments, a thickness of electrode 145-1 is between about 250 Åand about 350 Å. In some embodiments, a thickness of electrode 145-1 isbetween about 275 Å and about 325 Å.

Electrode 145-1 can be designed to cover the whole lateral surface(surface interfacing electrode 145-1) of the light emitting subpixel145-2 in order to provide a uniform current density to the lightemitting subpixel 145-2. However, in some embodiments, area of a lateralsurface of the electrode 145-1 can be different from the lateral surfaceof the light emitting subpixel 145-2. Electrode 145-1 has a width w,which is measured in a direction substantially vertical to the stackingdirection of layer 12 and layer 14 in FIG. 1. In some embodiments, thewidth w is not greater than 8 um. In some embodiments, the width w isnot greater than 5 um.

In some embodiments, the light emitting subpixels can emit at leastthree different colors, red, green, and blue. In some embodiments, eachlight emitting subpixel has a lateral width substantially equal to thewidth, w, of the electrode 145-1.

Adjacent light emitting units 145 are separated with a space s. Thespace s can be measured from adjacent electrodes 145-1 or adjacent lightemitting subpixels 145-2 depending on the design. In some embodiments,space s is between about 2 nm and about 100 um. In some embodiments,space s is not greater than about 50 um.

From FIG. 2, person with skill in the art should appreciate that theelectrode is only disposed on a limited area, which may be substantiallyto the area of the corresponding light emitting subpixel. Thecorresponding light emitting subpixel is defined as the light emittingsubpixel disposed right under the electrode. In other words, as long asthe electrode can supply uniform electric current to the light emittingsubpixel, the area or width of the electrode is preferred to be less.For some embodiments, the area of the electrode is designed to be justgreat enough to cover the lateral surface of the corresponding lightemitting subpixel.

The electrode design mentioned above is called a patterned electrodedesign. Instead of a blanket electrode to substantially cover thesurface 140, the present disclosure use patterned electrode to minimizereflection of lights from the ambient, which usually enter into thedevice 10 through the window layer 18 in FIG. 1. Entered ambient lightmight be reflected by the patterned electrodes but the reflection can beneglected from a human's eye since the width of the each electrode issmall, not greater than 8 um.

FIG. 5 is a cross sectional view along line BB in FIG. 3. Numeral labelsused in FIG. 4 represent same elements and are not repeatedly introducedherein. In some embodiments, the stopper 147 has a thickness t, whichmay be greater than the total thickness of an adjacent electrode 145-1and light emitting subpixel 145-2. While stacking layer 16 or layer 18over the light emitting layer 14 as in FIG. 1, layer 16 or layer 18 maycontact the stopper 147 to prevent the layer 16 or layer 18 fromtouching the electrode 145-1. Therefore, damage is avoided when a useris pressing the layer 18 or layer 16. Insulation material can be filledinto the space between the stopper 147 and the electrode 145-1.

FIG. 6 is a cross sectional view along line CC in FIG. 3. The opticalsensor 150 is disposed adjacent to the light emitting subpixel 145-2. Inthe present embodiment, the optical sensor 150 is disposed on thestopper 147. The optical sensor 150 is configured to detect theintensity of light emitted from the light emitting subpixel 145-2. As inFIG. 3, each optical sensor 150 is configured to detect the intensity ofone light emitting subpixel 145-2, which may be most adjacent to thatoptical sensor 150. As in FIG. 6, the light emitting subpixel 145-2right to the optical sensor 150 is designated.

In some embodiments, for an array of light emitting subpixels, eachlight emitting subpixel in the array is assigned with an optical sensor.Each optical sensor can monitor the performance of a corresponding lightemitting subpixel in a real time mode. Therefore, if a light emittingsubpixel is found to be under-performed, for example, lower intensity,by the corresponding optical sensor, compensation current can be addedto the light emitting subpixel in order to bring the performance back todesired value. The optical sensor can be further electrically connectedto a driver, which can decide when and how to supply a compensationcurrent to the light emitting subpixel. In some embodiments, thecompensation is performed either in active or offline mode.

The optical sensor 150 can be electrically connected to the substrate 12or the TFT layer 12 a. Performance of light emitting subpixel detectedby the optical sensor 150 can be converted into electrical signal, whichis delivered to the substrate 12 or the TFT layer 12 a. As in FIG. 6A,the electrical signal from the optical sensor 150 can be conducted tothe TFT layer 12 a either through a via 160 or a conductive trace 162.Via 160 can be formed in the stopper 147 as shown in the drawing. Theelectrical signal from the optical sensor 150 can be conducted to theTFT layer 12 a or other location through a conductive trace 164. In someembodiments, the TFT layer also includes a circuitry to measure theperformance of the light emitting subpixel.

FIG. 7 shows another embodiment having a second optical sensor 152. Thesecond optical sensor 152 is disposed on an insulation layer 148, whichis disposed to surround the electrode 145-1 and light emitting subpixel145-2. The insulation layer 148 can be configured as filling inserted inthe space between adjacent light emitting units. The insulation layer148 can be configured as filling inserted in the space between lightemitting unit and the stopper. In some embodiments, the top surface 148a of the insulation layer 148 is planarized in order to provide asubstantially flat surface for the second optical sensor 152 disposedthereon. In some cases, the top surface 148 a is configured to be intouch with layer 16 or layer 18.

The second optical sensor 152 is designed to detect the intensity ofambient light entering into the device 10. The current into lightemitting unit can adjusted according to the intensity detected by thesecond optical sensor 152. The second optical sensor 152 can be rightabove the light emitting unit or can be shifted. In some embodiments,there is only one second optical sensor 152 in the device 10. In someembodiments, there is only one second optical sensor 152 in the device10. In some embodiments, there are several second optical sensors 152and each second optical sensor 152 is designated to one light emittingunit.

In some embodiments, the optical sensor can be designed as shown in FIG.8A. The optical sensor 153 is a two-sided sensor having one sensor 153 aon surface and one sensor 153 b on surface. The sensor 153 a facing thewindow layer 18 is configured to detect the entered ambient light. Thesensor 153 a facing the electrode 145-1 and light emitting subpixel145-2 is configured to detect the light emitted from the light emittingsubpixel 145-2. The two sided optical sensor may be a compositestructure having an insulation layer such as oxide disposed between twosensing area.

FIG. 8B depicts another embodiment showing an insulation film 149 isdisposed over insulation layer 148. The insulation layer 148 isplanarized before film 149 disposed thereon. A sensor 153 b is disposedin the insulation layer 148 and facing the light emitting unit 145 todetect the intensity of light emitting subpixel 145-2. A sensor 153 a isdisposed over film 149 to detect the intensity of ambient light. In someembodiments, film 149 is planarized before the sensor 153 a disposedthereon.

The optical sensor can be made with optical sensing material such as Mn,Zn, Mg, S, etc. In some embodiments, the optical sensor includes a ZnScompound disposed on an insulation substrate. The insulation substratecan be silicon oxide, silicon oxide, etc.

Besides the above advantages, some other circuits such as driver ortouch sensor can be inserted between the light emitting units byshrinking down the size of the electrode 415-1 and light emittingsubpixel 145-2. Another example described below can further facilitate aperson with skill in the art to appreciate how the design window isimproved.

FIG. 9 is a cross sectional view depicting another embodiment of deceive10. A structure 210 is disposed over the insulation layer 148. Thestructure 210 can be configured as a part of a touch sensor. In someembodiments, the structure 210 is a capacitor. In some embodiments, thestructure 210 is a resistor. In some embodiments, the structure 210 is aconductive trace connected with a capacitor or a resistor at one end.

Structure 210 can be embedded in layer 16 or 18 when it is configured asa part of a touch sensor. In some embodiments, the structure 210 has alower light transmittance to the light emitting subpixel 145-2 than theelectrode 145-1. In such case, the structure 210 is preferred to bemisaligned with the light emitting subpixel 145-2 or the electrode 145-1from a top view perspective.

FIG. 10 illustrate a top view of one embodiment of several differenttypes of structures disposed over light emitting units 145. There are atleast three different tiers stacking along the thickness direction. Thelight emitting units 145 are in the bottom and structures 210 a, 210 b,and 210 e are between the light emitting units 145 and structures 210 c,210 d, and 210 f Structure 210 e is a conductive trace connectingstructures 210 a, 210 b. Structure 210 f is a conductive traceconnecting structures 210 c, 210 d. Structures 210 a, 210 b can be acapacitor so a resistor. Structures 210 c, 210 d can be a capacitor so aresistor.

Each structure is surrounded by light emitting units 145 and notoverlapped with the light emitting units 145. Therefore, light emittedfrom the light emitting unit 145 can efficiently reach the window 18without being blocked by the structures. Therefore, shrinking the sizeof the light emitting unit is not only to provide more opportunities todispose optical sensor to real monitor the performance of each lightemitting unit 145, but also provide more space to dispose otherfunctional structures while still meeting the requirement of highdensity.

The foregoing outlines features of several embodiments so that personshaving ordinary skill in the art may better understand the aspects ofthe present disclosure. Persons having ordinary skill in the art shouldappreciate that they may readily use the present disclosure as a basisfor designing or modifying other devices or circuits for carrying outthe same purposes or achieving the same advantages of the embodimentsintroduced therein. Persons having ordinary skill in the art should alsorealize that such equivalent constructions do not depart from the spiritand scope of the present disclosure, and that they may make variouschanges, substitutions and alternations herein without departing fromthe spirit and scope of the present disclosure.

1. A light emitting device, comprising: a substrate; and a lightemitting unit over the substrate, wherein the light emitting unitincludes: a light emitting subpixel; and an electrode stacking on thelight emitting subpixel along a vertical direction, the electrodeincluding a width measured in a horizontal direction perpendicular tothe vertical direction and the width is not greater than about 8 um. 2.The light emitting device in claim 1, wherein the electrode is a cathodeof the light emitting unit.
 3. The light emitting device in claim 1,further comprising an optical sensor adjacent to the light emitting unitand configured to detect emission intensity of the light emitting unit.4. The light emitting device in claim 3, further comprising an array ofthin film transistors (TFT) under the light emitting unit and theoptical sensor is electrically connected to the TFT.
 5. The lightemitting device in claim 1, further comprising a stopper adjacent to thelight emitting unit, wherein, along the vertical direction, the stopperhas a thickness being greater than a thickness of the light emittingunit.
 6. The light emitting device in claim 5, further comprising athrough via in the stopper.
 7. A light emitting device, comprising: asubstrate; and an array of light emitting units over the substrate,wherein each light emitting unit of the array includes: an electrode;and a light emitting layer between the electrode and the substrate,wherein a horizontal width of the electrode is substantially equal to ahorizontal width of the light emitting layer.
 8. The light emittingdevice in claim 7, further comprising an insulation material filling aspace between adjacent light emitting units.
 9. The light emittingdevice in claim 7, further comprising a conductive trace to connectelectrodes in a string.
 10. The light emitting device in claim 7,further comprising an array of optical sensors, wherein each of theoptical sensors is assigned to a corresponding light emitting unit. 11.The light emitting device in claim 7, further comprising an array ofstoppers, wherein each stopper is between two adjacent light emittingunits.
 12. The light emitting device in claim 10, further comprising aconductive trace electrically connecting each optical sensor to acircuit in the substrate.
 13. The light emitting device in claim 7,further comprising a touch sensor over the array of light emittingunits, and an insulation layer between the touch sensor and the array oflight emitting units.
 14. The light emitting device in claim 13, whereinthe touch sensor is surrounded by a plurality of light emitting unitsfrom a top view perspective.
 15. The light emitting device in claim 14,wherein the touch sensor is laterally offset from the plurality of lightemitting units from a top view perspective.
 16. The light emittingdevice in claim 7, further comprising an array of optical sensors overthe array of light emitting units, wherein the array of optical sensorsare configured to detect ambient light emitted into the light emittingdevice.